HashMap Sharing object issue

I am having the issue with the HashMaps, sharing the object. All the nested HashMaps have the same values. How do I overcome this issue? How do I create the HashMaps so they are independent from one another?

This below is my DTO, my first Integer object is going to range from 0-11, representing the months. The String represents country codes (i.e, "GB"), and the second Integer represents total amount of people. Meaning that value will be added to.

Below is Where I am trying to create the HashMaps. I am putting 0 to all first before I start adding values to them because certain months don't have any value but I need it to be 0. Obviously the below is not working.